In FEM, what is the characteristic of the problem with the functional Iv(v) representing governing equations of steady viscous incompressible flows?

• A. It is subjected to constraint ( frac{ partial v_x}{ partial x}+ frac{ partial v_y}{ partial y} )=0
• B. It is an unconstrained problem
• C. It can be reformulated as a constrained one, by using the penalty method
• D. It cannot be reformulated as an unconstrained one, by using the penalty method